1. Field of the Invention
The present invention relates to an improved emulsion polymerization process utilizing ethylenically unsaturated amine salts of sulfonic, phosphoric and carboxylic acids. More specifically, the invention relates to emulsion polymerization processes which utilize ethylenically unsaturated amine salts of alkylbenzene sulfonic acids, alkyl olefin sulfonic acids, alkyl alcohol sulfuric acid esters, or alkoxylated alkyl alcohol sulfuric acid esters, fatty acids, and fatty phosphate acid esters, or mixtures thereof, to form polymers, discrete solid polymeric particles and latexes. Additionally, the present invention relates to the use of the salts to impart improved adhesion, hydrophobicity, resistance to film yellowing, scrubability, anti-blooming, hydrolytic stability and shear stability characteristics to polymer emulsions and latex formulations.
2. Description of the Related Art
The emulsion polymerization of ethylenically unsaturated monomers to form discrete solid polymeric particles for use in coating, sealant, adhesive and/or elastomer (CASE) applications is well known to the art. Conventional emulsion polymerization of ethylenically unsaturated monomers employs one or more water soluble surfactants to emulsify the monomers and the resulting polymer products, i.e., latexes. The monomers used in emulsion polymerization reactions are generally water-insoluble, but in some cases may be water-soluble. During a typical emulsion polymerization, a surfactant is used to suspend small portions of monomer in a continuous or semi-continuous aqueous phase. Typically, the monomer molecules are suspended as small spheres in the aqueous phase, wherein the polymerization takes place within the small spheres. The water soluble surface active agents, i.e., surfactants, typically utilized in emulsion polymerization reactions are anionic, nonionic, and cationic surfactants or a mixture thereof.
The polymeric particles formed by the emulsion polymerization process are typically utilized in coating, sealant, adhesive and/or elastomer (CASE) applications. In a traditional emulsion polymerization reaction, the surfactant does not become chemically bonded to the polymeric particles by carbon-carbon bond formation but rather remains in the polymeric particle product solution after the emulsion polymerization reaction is complete, i.e., all of the monomer(s) is reacted. The unreacted surfactant can have a detrimental effect on the polymer product solution, as it can interfere with the performance of such polymerization products in CASE applications; the suspension of polymeric particles may become destabilized over time and undergo unwanted coagulation. The unreacted surfactant may cause unwanted pealing of a latex paint coating on a substrate, and decreased moisture and scrubability resistance in other various CASE applications. Additionally, residual surfactant can cause an undesirable xe2x80x9cbloomingxe2x80x9d that leads to surface irregularities in a resulting CASE material that is applied to a substrate.
Several proposals have been made in the prior art to employ a polymerizable surfactant as the surface active agent during an emulsion polymerization reaction. U.S. Pat. No. 5,478,883 (incorporated herein by reference in its entirety) describes the use of ethylenically unsaturated polymerizable water-soluble nonionic surfactants formed by the reaction of a diallylamine compound with ethylene oxide, propylene oxide or butylene oxide, in emulsion polymerization reactions. Similarly, U.S. Pat. No. 5,162,475 (incorporated herein by reference) provides alpha-beta ethylenically unsaturated poly(alkylenoxy) polymerizable surface active compounds for use in emulsion polymerization. For additional examples of polymerizable surfactants for use in emulsion polymerization processes, see U.S. Pat. Nos. 4,377,185 and 4,049,608.
Non-polymerizable surfactant solutions to the traditional problems encountered in performing an emulsion polymerization process are numerous. U.S. Pat. No. 3,941,857 describes the use of epoxy resins which react with the residual anionic, cationic or nonionic surfactant. Polymerizable compounds such as allyl alcohol (and esters thereof) have been found to be ineffective due to the formation of undesirable high levels of coagulum in the final emulsion polymerization product. Additionally, see U.S. Pat. No. 4,224,455.
Thus, there is a need for an emulsion polymerization process for forming polymers and discrete polymeric particles that are well suited for use in coatings (e.g., latex paints, electro-deposition, container, paper and paperboard, can coatings, industrial coatings, automotive coatings, textile coatings), adhesive (e.g., water- and non-water borne adhesives, pressure sensitive adhesives, binders), sealant (e.g. floor finishes, films, binders, non-woven binding materials such as carpet backing, glass fibers) and elastomer (CASE) applications.
The present invention utilizes a novel group of compounds in the form of ethylenically unsaturated amine salts of sulfonic, phosphoric and carboxylic acids, which display surface activity, i.e. they are surfactants. It has been discovered that these compounds function as reactive surfactants, i.e. surface active agents in polymerization processes, particularly emulsion polymerization processes. The surface active agents of the present invention are capable of polymerizing with themselves (to form homopolymeric surface active agents) and/or are capable of co-polymerizing with other ethylenically unsaturated monomers of the type which are commonly employed in polymerization processes. The polymerizable surface active agents utilized in the present invention are prepared from readily available, economical raw materials, and generally, their preparation does not require any special handling or equipment.
Accordingly, an improved method is provided for forming polymers utilizing polymerizable surface active agents detailed herein. Generally, the improved method comprises:
a) preparing a mixture comprising:
i) at least one ethylenically unsaturated monomer;
ii) at least one polymerizable, surface active agent;
xe2x80x83wherein the polymerizable, surface active agent is a salt or quaternary nitrogen compound comprising:
a) at least one acid, wherein the acid is a sulfonic acid, a carboxylic acid, or a phosphoric acid, or a mixture thereof; and
b) at least one nitrogenous base, wherein the nitrogenous base contains at least one nitrogen atom and at least one ethylenically unsaturated moiety; and
b) polymerizing the mixture;
xe2x80x83wherein the polymerizable, surface active agent is capable of polymerization with itself, copolymerization with the ethylenically unsaturated monomer or co-polymerization with a partially polymerized polymer particle. Somewhat preferably, the nitrogen atom is linked covalently, directly or indirectly, to the ethylenically unsaturated moiety of the nitrogenous base.
The polymers prepared utilizing the polymerizable surface active agents of the present invention may be used as the primary resin component or a minor resin component of a resin mixture which is used to prepare latexes, coatings, adhesives, sealants, elastomers, binders, inks, floor finishes and the like. A polymer is defined herein as a product produced by polymerizing two or more monomers, which may be the same or different. Additionally, the polymer may have incorporated into it, surface active agent monomers and/or homopolymeric surface active agents. The various final compositions, application and polymer products described herein may contain various optional ingredients such as fillers, pigments, colorants, solvents, plasticizers, antioxidants, curing agents, thickeners, non-polymerizable surface active agents (surfactants), preservatives, wet strength additives, and the like.
The present invention provides an improved polymerization process for forming polymers, wherein the polymerizable surface active agent used in the polymerization reaction does not interfere with the quality of the CASE applications. Various classes of polymers formed in the present invention, upon application to textiles, fabrics, and other substrates, may reduce the shrinkage of cotton fabrics, cotton/polyester blend fabrics, cotton/rayon blend fabrics, rayon fabrics, and cellulosic or cellulosic/synthetic blend fabrics.
The present invention provides an improved polymerization process, for making suspension or dispersions of polymers which exhibit enhanced mechanical stability and the ability to withstand freezing and thawing while at the same time retaining good dispersion or suspension.
The present invention provides an improved polymerization process, wherein the resulting polymers exhibit/impart improved adhesion of a CASE to a substrate, e.g. they are substantially resistant to pealing and cracking.
The present invention provides an improved polymerization process, wherein the resulting polymers exhibit/impart improved anti-yellowing properties when employed in a CASE application.
The present invention provides an improved polymerization process, wherein the resulting polymers exhibit/impart improved scrubability properties of a CASE application.
The present invention provides an improved polymerization process, wherein the resulting polymers exhibit/impart improved solvent resistance properties when employed in a CASE application.
The present invention provides an improved polymerization process, wherein the resulting polymers exhibit/impart improved film rewet properties when employed in a CASE application.
The present invention provides an improved polymerization process, wherein coatings formed, using the polymers of the present invention, remain uniform and stable upon the passage of time and/or exposure to moisture at ambient or elevated temperature.
The present invention provides polymers suitable for use in coating, adhesive, sealant and/or elastomer (CASE) applications. The polymers may be in a variety of forms, such as, for example, solids, flakes, powders, semi-solids, thick pastes, flowable/pumpable pastes (i.e. G-phase pastes), liquids, gels, xe2x80x9cringingxe2x80x9d gels, dilute or concentrated solutions and the like. The polymers may be spray dried, flaked, extruded, or the like.
The present invention additionally provides homopolymeric surface active agents comprised of polymerized, polymerizable surface active agents or blends of polymerizable surface active agents. These homopolymeric surface active agents are useful in the polymerization processes detailed herein. The present invention further provides homopolymeric surface active agent/polymerizable surface active agent blends comprised of partially polymerized, polymerizable surface active agents and non-polymerized, polymerizable surface active agents. These homopolymeric/polymerizable surface active agent blends are also useful in the polymerization processes detailed herein.
The improved polymerization process of the present invention preferably does not require the use of a surfactant which contains residual formaldehyde or other low molecular weight volatile organic compounds. However, while not usually desirable, low molecular weight volatile organic compounds and/or residual formaldehyde may be present in the polymerization products of the present invention. Further, the polymerization process of the present invention provides latexes with improved shear stability, improved pH stability, improved shelf storage stability and improved ease of viscosity modification.
The polymerizable surface active agent may be added to the mixture in a batch mode (i.e. all at once), a continuous mode (i.e. by addition of an amount of the polymerizable surface active agent throughout the polymerization) or in a semi-continuous mode (i.e. addition of portions of the polymerizable surface active agent at various times during the polymerization).
The polymerizable surface active agents utilized in the present invention are generally formed by combining at least one acid, wherein the acid is a sulfonic acid, a carboxylic acid, or a phosphoric acid, or a mixture thereof, with a nitrogenous base, wherein the nitrogenous base contains at least one nitrogen atom and at least one ethylenically unsaturated moiety. The polymerizable surface active agents of the present invention generally contain a quaternary nitrogen atom and are in the form of salts or quaternary nitrogen compounds.
Various functional groups may be incorporated in the polymerizable surfactants of the present invention, in either the acid or the nitrogenous base, to form specialty polymerizable surface active agents. These specialty polymerizable surface active agents may posses various properties such as, for example, biocidal activity, herbicidal activity, pesticidal activity, anti-static activity and the like, either before or after polymerization with known monomers or polymerization with themselves. Additionally, the polymerizable surface active agents of the present invention may be utilized in forming biodegradable polymers, photoreactive polymers, sunscreen enhancing polymers, fabric softening polymers, polyol polymers, ophthalmic polymers, lubricants and the like.
These and other objects and advantages, as well as the scope, nature, and utilization of the claimed invention will become apparent to those skilled in the art from the following detailed description and claims.